1. Field of the Invention
The present invention relates to a method, system, and program for generating output indicating offset track errors in a storage system.
2. Description of the Related Art
Computer hard disk drives include one or more disks of magnetic storage medium and a disk drive head assembly to read and write data on the magnetic storage medium. Magnoresistive (MR) heads typically include a write element comprised of a thin film inductive head and a read element comprised of a sensor. In a magnetic disk storage medium, data is stored on concentric circular tracks on the disk, where each concentric track is divided into sectors. To write data, the head is directed to write data at the center of the track. If the head is not accurately positioned at the center, then data is written at offsets from the center of the track. Such offset track writing of data can spill over onto the adjacent concentric tracks. The situation where offset writing on one track affects the data on another track is referred to as track misregistration or track squeezing. Track misregistration is typically caused by positioning irregularities of the head with respect to the rotating disk, track interference, and head (magnetic) domain noises. Other causes of errors in disk drives are described in xe2x80x9cMagnetic Disk Drive Technology: Heads, Media, Channel, Interfaces, and Integration,xe2x80x9d by Kanu G. Ashar (1997), which publication is incorporated herein by reference in its entirety.
Current techniques for measuring head positioning irregularities involve analyzing the signal from the head when reading data from a sector. Analysis of the signal can indicate the amount of misregistration on track. In the prior art, an oscilloscope would be used to measure the read signal to determine whether the amplitude of the read signal is unusually high or low, indicating that the head was writing the data at an offset from the track. However, a determination cannot be made as to whether a track with offset conditions is being affected by irregularities at an adjacent track or the irregularities occurred on the track being measured. Further, this inability to analyze in detail the affects of offset track writing makes it more difficult to diagnose and correct the cause of offset track writing.
This inability to diagnose with particularity the causes and source of offset track writing is especially troublesome for high end disk manufacturers, such as server class disk files. Often when customers encounter an error that cannot be corrected using the error checking codes (ECC), the customer will want to know the specific cause of the error. A general determination of track misregistration may not be sufficient to pinpoint the particular problem, such as head writing irregularities. This inability to pinpoint the problem with particularity may not only make it more difficult to diagnose and correct the problem with other disks, but also may frustrate the customer""s demand for specific information and assurances. Providing detailed diagnosis of the problem is especially important in situations where the customer is an original equipment manufacturer (OEM) purchasing mass quantities of the disk file and insists on knowing specific problems with the disk file, and not just general explanations of the problems.
Thus, there is a need in the art for disk analysis tools that provide a more fine grained analysis of the track to allow for a more detailed analysis of head irregularities and their affect on a particular track.
To overcome the limitations in the prior art described above, preferred embodiments disclose a method, system, and program for generating and displaying disk drive performance data. A center stripe of one sector of one track on a recordable surface is read. An indication is made indicating whether the read operation to the center of the sector succeeded. Each offset stripe from the center of the track in the sector within the track is read and indication is made as to whether each read operation to each offset stripe succeeded. Output in human observable format is generated indicating whether each offset stripe and the center stripe for the sector and track were read successfully or could not be read.
In further embodiments, indication is made as to a number of the track, wherein the track includes a plurality of sectors having sector numbers. For each sector in the track, each center stripe and offset stripe is read and indication is made as to whether each read operation succeeded or failed. In such case, the generated output indicates for each sector whether each offset stripe and center stripe of each sector was read successfully or could not be read.
In still further embodiments, the human observable format comprises a human readable medium. In such case, generating the output further comprises generating the sector number of each sector in a separate row in the human readable medium and generating in each row having one sector number the output indicating whether each offset and center stripe was read successfully or could not be read.
Preferred embodiments provide a disk analysis tool for testing each offset stripe within a track to determine the affects of offset track writing. Preferred embodiments present to the disk designer information indicating the results of reading the offset stripes within a track by sector. The output results allow the disk designer or other person analyzing the data to analyze the affects of offset track writing within a particular track and analyze adjacent tracks to consider the squeeze affects of offset track writing on adjacent tracks. This detailed level of output allows the disk designer to better diagnose and correct problems with the disk head to avoid future offset track writing problems.